Field of the Invention
This invention relates to a channel-selection control system for a PLL (phase-locked loop) type synthesizer receiver, and more particularly to a channel-selection control system for a frequency synthesizer type receiver, which is operative in association with a programmable divider with a variable division ratio, constituting a part of a PLL circuit of the frequency synthesizer type receiver, and capable of detecting and receiving, among plural broadcasting waves, one which is in good reception condition and whose level exceeds a preset reference level, in a broadcasting system wherein one broadcasting program is transmitted in the form of broadcasting waves of different frequencies.
In some broadcasting system, a plurality of channels have different broadcasting contents or programs, respectively, and each of the broadcasting content or program is transmitted at different frequencies. For example, according to Nihon Shortwave Broadcasting, the first channel (the first program) uses frequencies of 3,925, 6,055 and 9,595 MHz and the second channel (the second program) uses frequencies of 3,945, 6,155 and 9,760 MHz for broadcasting the first and the second program, respectively. In such a broadcasting system, it is very effective to automatically detect and receive, among broadcasting waves, one which is in good reception condition and whose level exceeds a preset reference level.